Apparatus available so far for testing dielectric materials or capacitors either operates at one frequency only, or else takes a particularly long time to perform the tests.
The present invention seeks to provide a novel method and apparatus for rapidly obtaining the frequency response of said dielectric materials or capacitors over a wide range of frequencies, for example from 10 Hz to 1 MHz.
The present invention thus enables a very much more thorough quality control to be performed.
More precisely, the present invention seeks to determine the parameters Ri and Ci of a capacitor or of a dielectric material as represented by the Foster model, as shown in the accompanying FIG. 1.
It is recalled that Foster's theorem shows that a non-ideal capacitor may be represented by an equivalent network made up of resistances and capacitances. As shown in the accompanying FIG. 1, this equivalent network comprises a plurality (n) of parallel-connected branches, each of which is constituted by a resistance Ri and capacitance Ci connected in series, together with two special branches which are likewise connected in parallel and which take limiting conditions into account. These special branches are respectively constituted by a pure capacitance C.infin. and by a pure resistance Rs.
This leads to the capacitance of a capacitor being written in the form: ##EQU1## where .tau.i=Ri.Ci.
The aim of the present invention is consequently to determine the above-mentioned parameters C.infin., Rs, Ri and Ci.